This application claims the benefit of German patent application 102 01 577.5, filed Jan. 17, 2002, herein incorporated by reference.
The present invention relates to a spinning device for producing a spun yarn by means of a circulating air flow.
A spinning device for producing a spun yarn by means of a circulating air flow is known from German Patent Publication DE 199 26 492 A1. A sliver to be spun is drawn into a nozzle body and passes a sliver guidance device. The sliver guidance device has sliver guide elements, which are spaced apart from each other and permit the free passage of a core fiber bundle. The sliver is subjected to an air flow circulating around the sliver at the inlet opening of a spindle. The free fiber ends of the sliver are wrapped around the conical spindle head by the circulating airflow at the inlet opening of the spindle. In the course of drawing the sliver into the hollow spindle, these fiber ends wrap themselves in a spiral shape to form wrapped fibers around the sliver, whereby a yarn is produced from the sliver and removed through the hollow spindle.
German Patent Publication DE 40 36 119 C2 also shows a device for producing a spun yarn by a circulating air flow by which free fiber ends of the sliver are wrapped around a conical spindle head at the inlet opening of the spindle by the circulating air flow. With this spinning device, the sliver guidance device is located inside the running fiber strand, so that the fibers of the sliver are arranged at the circumferential surface of the sliver guidance device.
Continuously increasing demands in regard to productivity and yarn properties are made on modern spinning frames. Such spinning devices, known from above-referenced. German Patent Publication DE 199 26 492 A1, or in another embodiment from above-referenced German Patent Publication DE 40 36 119 C2, are suitable for achieving high production speeds, along with good yarn properties. It is all the more bothersome if in the course of starting the processes at high withdrawal speeds, such as are employed during normal spinning operations, repetitions of the start of the spinning process are often made necessary because, at these high yarn speeds the spinning start process takes place relatively uncontrolled and with a greatly reduced assurance of a satisfactory spinning start.
It is known from rotor spinning to clearly lower the withdrawal speed during the spinning start process in comparison with the spinning operation in order to achieve a more easily controlled spinning start process and therefore greater spinning start assurance. However, if an attempt is made to utilize this type of operation from rotor spinning and to operate a circulating air flow spinning device at a lowered withdrawal speed of the yarn in the spinning start phase, a yarn is temporarily created thereby whose yarn strength could be unsatisfactory. Such yarn sections of reduced strength constitute undesired weak points. This increases the danger of yarn breaks and considerably reduces the interference-free processing of the yarn. In the least advantageous case a yarn break may occur already in the spinning start phase. This has very disadvantageous consequences with regard to the intention of achieving a good yarn quality along with high productivity when employing the air spinning method. It is therefore customary to perform the spinning start process at the high withdrawal speeds of the normal spinning operation and in the course of this start process to accept the disadvantages of frequent repetitions of the spinning start process.
The above described problems cannot be overcome by the known prior art, such as disclosed in German Patent Publications DE 199 26 492 A1 or in DE 40 36 119 C2.
It is accordingly an object of the present invention to further develop the above mentioned prior art to provide improved devices for producing a spun yarn employing a circulating air flow.
Basically, the spinning device of the present invention produces a spun yarn by a circulating air flow, and for this purpose comprises a housing having an inlet opening for receiving a sliver, at least one sliver guidance element arranged downstream of the inlet opening, a hollow spindle through which a formed yarn is withdrawn, the spindle having a conical spindle head, and openings in the area of the spindle inlet for injecting into the housing a circulating air flow comprised of a linear airflow component essentially in a yarn traveling direction and a twisting airflow component essentially in a helical orientation about the yarn for wrapping free fiber ends of the sliver helically around the spindle head to subsequently be wrapped around the yarn at an acute angle in respect to the yarn traveling direction as the yarn is drawn off through the spindle. In accordance with the present invention, an adjustment device is provided for adjusting at least the linear airflow component as a function of the withdrawal speed of the yarn and controlling a helical wrapping angle of the fiber ends around the spindle head and the acute angle of wrapping of the fibers around the yarn; and a control device is provided for controlling the adjustment device between a setting for the spinning start process and at least one setting for normal spinning operations. For example, the injector effect of air nozzles or the vacuum in the housing can contribute to forming the air flow. At least a part of the air flow in the yarn running direction can be formed by air entering the inlet opening of the housing together with the sliver.
In accordance with one embodiment of the present invention, the adjustment device includes a positionable cover for the inlet opening such that the position of the cover determines the cross section of the inlet opening. The greater the cross section of the inlet opening, the greater the amount of air entering the housing together with the sliver, and therefore the proportion of the linear component of the circulating air flow in the area of the spindle head. If the cross section is reduced, the amount of air is correspondingly reduced. The linear component of the air flow is advantageously set by controlling the cross section of at least one air inlet opening for this air flow. A control of the air drawn in through the inlet opening offers the advantage that no additional amount of air needs to be made available to be blown into the housing.
An alternative embodiment for setting the linear component of the air flow is provided by a bypass of the inlet opening of the fiber conduit in the housing, which is directed in the yarn traveling direction, and whose cross section can be adjusted by means of the adjustment device. In spinning frames with a plurality of work stations, considerable costs can be avoided by means of the mutual advantage of these embodiments by not having to provide additional amounts of air.
In a further alternative embodiment, the housing has at least one injection conduit, which is directed in the yarn traveling direction and is connected with the compressed air source. The adjustment device is equipped for setting the air pressure of the supplied air. In this manner, the adjustment of the linear component of the air flow occurs in a particularly simple and rapid manner through the regulation of the pressure of the air supplied by the compressed air source. In particular, no mechanical devices are required, whose function could be reduced or hampered by dust or flying fibers.
The linear component of the air flow is advantageously set in such a way that the angle at which the wrapped fibers have been placed around the withdrawn yarn lies in the range between 20xc2x0 to 35xc2x0, preferably at 27xc2x0. It is possible to empirically determine how the adjustment device must be set in each individual case for achieving the greatest yarn strength possible, and to store the appropriate settings, for example in a data memory of a control device, for retrieval and use in connection with identical spinning parameters. For this purpose, the control device includes a data memory for storing yarn data and is connected to a line through which the yarn data can be input to the memory. The adjustment device can be controlled as a function of the yarn data.
The provision of a single drive mechanism for each spinning station makes it possible to be able to immediately perform every spinning start process at each spinning station in the manner in accordance with the invention independently of other spinning stations of the spinning frame. Downtimes are reduced in this way.
It is possible by means of the invention to prevent an impermissible drop of the yarn strength during the spinning start process, which is performed with a clearly reduced withdrawal speed in comparison with the normal spinning operation which ensues following the spinning start. The assured reliability of the spinning start process is increased. The tendency toward faults in the further processing of the yarn can be reduced. A high productivity, along with good yarn quality, can be achieved by means of the invention.
When using the device in accordance with the invention in connection with batch changes, it is possible in some cases to omit the exchange of the housing, or portions of the housing, for meeting the new yarn parameters.
Further details, features and advantages of the present invention will be explained and understood from the following description of preferred embodiments of the invention with reference to the accompanying drawing figures.